fix(access-logs): 修复概览域名筛选参数 hosts[] 被 Gin 忽略

Axios 默认序列化为 hosts[]=，Gin QueryArray("hosts") 读不到导致筛选失效；
后端兼容 hosts/hosts[]，前端改为重复键序列化。

internal/apps/openflare/observability/query_params_test.go

@@ -0,0 +1,57 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package observability
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestReadQueryStringArrayAcceptsHostsBracketForm(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	cases := []struct {
+		name string
+		url  string
+		want []string
+	}{
+		{
+			name: "axios brackets form",
+			url:  "/overview?hours=168&hosts%5B%5D=gist.arctel.de",
+			want: []string{"gist.arctel.de"},
+		},
+		{
+			name: "repeated hosts keys",
+			url:  "/overview?hosts=a.example&hosts=b.example",
+			want: []string{"a.example", "b.example"},
+		},
+		{
+			name: "single hosts key",
+			url:  "/overview?hosts=gist.arctel.de",
+			want: []string{"gist.arctel.de"},
+		},
+		{
+			name: "empty",
+			url:  "/overview?hours=24",
+			want: nil,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			w := httptest.NewRecorder()
+			c, _ := gin.CreateTestContext(w)
+			req, err := http.NewRequest(http.MethodGet, tc.url, nil)
+			require.NoError(t, err)
+			c.Request = req
+
+			got := readQueryStringArray(c, "hosts")
+			require.Equal(t, tc.want, got)
+		})
+	}
+}